Fruit flies in the Family Drosophilidae are pests in dwellings and commercial premises, wherever fruit or other vegetable matter is left exposed (Mallis 1969). In addition, fruit flies inhabit diverse natural habitats, and are the subject of considerable ecological study. Accordingly, there has been much effort directed to trapping fruit flies, either to control a pest problem or to capture subjects for research.
Fruit flies are strongly attracted to rotting fruit, in which microbial action results in the production of acetic acid. Thus ubiquitous household pests like Drosophila melanogaster have earned the common name vinegar flies (Mallis 1969). The association of fruit flies with yeasts is well known, and specific species of yeasts are found in the diet and alimentary canal of various Drosophila species (Phaff et al. 1956). Baits comprised of banana mash fermented by bakers' yeast have been used to attract fruit flies since the 1930's (Reed 1938; Spencer 1950; Phaff et al. 1956).
Considerable research has been directed at discovering the natural volatiles that attract fruit flies to their hosts, and incorporating them into lures for commercial traps. Early research disclosed the following attractants: ethanol, acetic acid, ethyl acetate and acetaldehyde (Barrows 1907; Hunter et al. 1937; West 1961). Building on this base, Zhu et al. (2003) found that overripe mango fruit produced several fruit fly attractive compounds, including: ethanol, acetic acid, amyl acetate, 2-phenylethanol and phenylethyl acetate. In cage bioassays, a synergistic 1:22:5 blend of ethanol, acetic acid and 2-phenylethanol attracted six times more D. melanogaster than any of the components alone. However, in a field test in a grocery store, traps baited with the three-component blend captured only 30% of the available fruit flies over a five day period. Proceeding further, Baker et al. (2003) teach that effective attraction of D. melanogaster can be obtained with compositions that can comprise: a volatile short-chain carboxylic acid (e.g. acetic acid), a volatile short-chain alcohol (e.g. ethanol), a volatile aryl-substituted alcohol (e.g. 2-phenylethanol), a nitrogen compound (e.g. indole or trimethylamine), a sugar (e.g. sucrose), a terpene compound (e.g. α-copaene), ethyl acetate, 2-phenylethylacetate and water.
One problem in using synthetic volatile compositions is that they do not mimic natural circumstances because they do not release carbon dioxide, which is a product of the metabolic action of yeast on a fermentable substrate in the presence of water (Simchoni and Shinitsky 2003). Using a more natural lure composed of fruit and yeast leads to another problem, however, because the rapid degradation of the fruit leads to an unpleasant rotten state. In addition, fruit flies can reproduce in a fruit lure, and the larvae (maggots) will exacerbate the unpleasantness in the eyes of many users.
The inventors herein reasoned that a novel solution to both of the above problems would be to use a dry fruit and yeast mixture, possibly in the form of a powder, which could be stored indefinitely prior to use. To activate the yeast, water could be added just before the lure was placed in a trap.
Water is a necessary component of certain toxic insect feeding baits, which do not include microorganisms. A humectant is a substance that promotes retention of moisture (American Heritage Dictionary 2003). Retention and slow release of water to prolong the acceptability of such toxic baits for termites requires the addition of a humectant, e.g. polyacrylamide (Rojas et al. 2003, 2004). We therefore also reasoned that a novel means of prolonging the bioactivity of an attractive lure for fruit flies would be to add a humectant to the powdered fruit and yeast mixture.
Fruits contain mainly the simple six-carbon sugar fructose, which is rapidly metabolized by yeasts. Thus, the longevity of a powdered fruit and yeast lure for fruit flies would also be limited by the availability of fructose, despite the presence of a humectant. Galactose is also a six-carbon sugar that occurs naturally as one of the products of enzymatic digestion of the 12-carbon sugar lactose, commonly called milk sugar. Because the flux through the galactose pathway is about three-fold slower than for fructose (Ostergaard et al. 2001), we reasoned that a second novel means of prolonging the bioactivity of an attractive lure for fruit flies would be to add a source of galactose, e.g. molasses or cheese whey, to the powdered fruit, yeast and humectant mixture.
Traps for fruit flies come in several forms. One recent design comprises an enclosed reservoir, containing a liquid lure and trapping fluid, and an entry port at the base of a funnel in the top of the trap, that is opened by puncturing before the trap is used (Muramatsu 1996). This trap is available commercially as the Natural Catch Plus Fruit Fly Trap (Natural Insect Control, Stevensville, Ontario, Canada). One modification of this design, the 960 Vector Fruit Fly Trap (Whitmire Micro-Gen Research Laboratories, St. Louis, Mo., USA), has holes in the lid, with a peel-off cover that is removed before use. A further modification of this design, the Dead Easy Fruit Fly Trap, involves a bottle containing the lure and trapping fluid, with a pull-out cap that opens an entry port (Dead Easy Pest Control, Victoria, BC, Canada). Other commercial traps involve a jar with a flip-top lid to provide entry for the fruit flies, combined with a lure that floats in water in which the flies are trapped, and a simple sticky band that is placed around a fruit lure on a flat surface (SpringStar LLC, Woodinville, Wash., USA). Do-it-yourself traps usually incorporate the same elements as the commercial traps, i.e. some kind of entry port and a reservoir in which the flies are captured in a “brew” (ABC Riverina, Wagga Wagga, New South Wales, Australia) or simply an enclosed air space. Containment traps of the Peters Trap Design, 1989, have not been used or adapted for catching fruit flies.
The first three reservoir commercial traps are opaque, and it is impossible to observe whether the traps have captured any flies. The SpringStar jar trap has a label that obscures visual observation of captured flies. It is easy to see captured flies on the SpringStar sticky trap, but there is no receptacle for a lure. All traps that use water as a catching medium may not be totally effective, because fruit flies are often light enough to float on the surface, even though detergent may be added to lessen the surface tension. We therefore judged that a further novel composition might comprise said powdered host substrate and yeast lure, with humectant and galactose extender, contained in a modified Peters trap that had the following characteristics: a transparent outer wall, a transverse dual port entry tube with a cut-away opening into the internal chamber (partially or completely severing the transverse tube), and a removable sticky trapping surface to replace the water trapping medium in the original design. Such a trap would have the advantages of: easy visual inspection of captured flies, containment of the lure and trapping surface inside the chamber of the trap, easily replaceable lures and trapping surface so the trap could be re-used, modification of trap size without any substantial design change, and elimination of spillage and build up of foul odour of the water trapping medium.
The foregoing examples of the related art and limitations related thereto are intended to be illustrative and not exclusive. Other limitations of the related art will become apparent to those of skill in the art upon a reading of the specification.